The present invention generally relates to a directional control system for a gantry type crane which is drivable in longitudinal and transverse directions. More specifically, the invention relates to a steering control system which enhances steering control by automatically switching steering control to a "leading" pair of wheels.
Mobile gantry cranes are generally known for lifting, loading, and moving heavy loads and containers. Such cranes are commonly used at shipping yards, railyards, construction sites, etc. A gantry crane typically has four corner-mounted wheels.
So that a gantry crane can be desirably maneuvered and positioned over an object to be lifted, at least one pair of wheels of the crane is typically steerable. Transverse movement has been found to be desirable under certain lifting circumstances, and therefore, cranes are known in which all four wheels may be turned in a transverse direction for side-to-side movement. For example, U.S. Pat. No. 5,180,070 discloses a crane in which all four wheels may be turned in a transverse direction.